Generally, semiconductor dies may be connected to other devices, such as printed circuit boards or even other semiconductor dies (e.g., in a flip chip configuration) using metallic bumps connected to conductive pads located on the semiconductor dies. These conductive pads can provide electrical input/output connections to active devices (e.g., transistor, capacitors, inductors, etc.) located on the semiconductor dies or even provide access to other dies through, e.g., through silicon vias (TSVs) that extend through the semiconductor die.
The metallic bumps may be, for example, solder bumps. These solder bumps may be capped onto the conductive pads through a process such as electroplating, in which the conductive pads are immersed in a precursor bath while an electrical current is applied to the conductive pads. The electrical current allows the solder bump to plate just the conductive pads without plating other non-conductive regions of the semiconductor die. Once the solder has been plated onto the conductive pads, the solder may then be heated until it reflows and forms into a solder ball. The solder ball may then be used to connect the semiconductor die to a printed circuit board or another semiconductor die.
However, the plating process is not an ideal method for forming these metallic bumps. In particular, the plating process is extremely complex with such process steps as immersion; application of an electrical current; monitoring and control of current, concentration of the immersion bath, and other process considerations; and the like. These process steps, in addition to being difficult to properly control and monitor, also increase the costs associated with the plating, which drives up the overall cost to manufacture the semiconductor die.
Additionally, by relying upon a plating process, the materials chosen for the metallic bump must be compatible with the plating process itself. As such, by utilizing a plating process, a manufacturer is also limiting the materials that may be used for the metallic bump. These materials may not be ideal, and may lead to a metallic bump that is less efficient than may be otherwise achievable.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.